Method of starting tubes through drawing die

ABSTRACT

A PRE-FORMED POINT MEMBER IS WELDED ONTO THE LEADING END OF A PIPE PRIOR TO COLD DRAWING OF THE PIPE AND RECOVERED FOR REUSE AFTER THE DRAWING OPERATION. THIS POINT MEMBER IS CAPABLE OF BEING COLD DRAWN THROUGH NUMEROUS REDUCING DIES WITHOUT BEING REPLACED.

United States Patent 5 [191 Katunich et al.

METHOD or STARTING TUBES THROUGH DRAWING DIE Inventors: Samuel Katunich, Baldwin Borough;

George C. McKelvey, Port Vue Borough, both of Pa.

United States Steel Corporation. Pittsburgh, Pa.

Filed: Jan. 17, 1973 Appl. No.: 324,275

Related US. Application Data Assignee:

Division of Serv No. 53,602, July 9, 1970, abandoned.

US. Cl 29/470.3, 72/283, 138/109, 228/2 Int. Cl B23k 27/00 Field of Search 29/470.3; 228/2; 72/283, 72/284; 29/181, 190, 498; 138/109 References Cited UNITED STATES PATENTS l/1891 Bcvington 29/4703 June 28, 1974.

Primary ExaminerJ. Spencer Overholser Assistant ExaminerRobert J. Craig Attorney, Agent, or Firm-Ralph H. Dougherty ABSTRACT A pre-formed point member is welded onto the leading end of a pipe prior to cold drawing of the pipe and recovered for reuse after the drawing'operation. This point member .is capable of being cold-drawn through numerous reducing dies without being replaced.

2 Claims, 6 Drawing Figures minimum m4 3.820.230

5 IIIIIIIIII I FIG. 5.

. l METHOD OF STARTING TUBFS THROUGH DRAWING DIE This is a division of U.S. Pat. application Ser. No. 53,602, filed July 9, 1970, now abandoned.

The present invention relates generally to cold drawing processes, and, more particularly, to an improved method of pointing tubes prior to drawing, and to a weldable point member for introducing tubes to drawing dies.

Conventional practice in the cold drawing of tubes requires that one end of each tube be pointed. That is, a portion of one end of the tube is sufficiently reduced in diameter to enter the opening in a drawing die, and for a sufficient length to protrude through the die and far enough beyond to enable the tube end to be firmly gripped in the jaws of a plier or gripping mechanism. After the drawing operation, the pointed portion of the tube is cut off and scrapped. Examples of tube drawing machines are disclosed by U.S. Pats. No. 718,671 and 1,951,073.

Pointing is conventionally accomplished by hot forging or hot rotary swaging. In either case the tube end must be heated to forging temperature prior to hot working. Differential strains result fromhot working or from cooling the forging temperature, and are accompanied by residual stress. Thus certain grades of steel require a stress-relieving heat treatment prior to cold drawing.

Conventional pointing operations often result in axial misalignment of the tube body and the point, and lack of symmetry of the point. These problems, and a differential between the cohesive strength of the tube body and pointed portion, and other characteristics, such as grain size, tend to cause the point to break during the drawing process. Where the tube is to be reduced in two drawing passes, the tube is usually pointed a single time. However, where the tube is to be drawn through more than two passes, it is generally re-pointed after each draw. The conventional pointing process lends itself to neither automation nor in-line processing. In the cold drawing of thin-walled tubes, especially those over three inches in diameter, the pointoften collapses.

It is the primary object of our invention to provide an improved method of pointing the end portion of a tube so that it can be drawn through a die.

It is another object to provide a point member for introducing a tube to a drawing die, which member is in accurate axial alignment with the tube body and is symmetrical.

It is a further object to provide a point member that will not collapse.

It is another object to provide a point member that enables a tube to be drawn through many passes without re-pointing.

It is another object to provide a strong tube point member that is capable of being attached to a tube during an in-line step of the drawing process, which step is capable of being automated.

It is a further object to provide a method of pointing tubes to be cold drawn without necessitating a heat to the end of the tube, and introducing it to the drawing apparatus.

FIG. 1 is a side view, partly in section, of a tube pointed in accordance with this invention being cold drawn.

FIG. 2 is a longitudinal-sectional view on a larger scale of a tubular pre-formed point attached to a tube.

FIG. 3 is a longitudinal-sectional view of an alternative embodiment in which the pre-formed point has a solid portion.

FIG. 4 is a longitudinal-sectional view of another alternative embodiment.

FIG. 5 is a longitudinal-sectional view of another alternative embodiment in which the point is partly conical.

FIG. 6 is a side view of yet another alternative embodiment in which the point has steps of increasing diameter.

Referring now to the drawings, reduction of tube 10 is accomplished by pulling it through die 12. The diameter of one end portion of point member 14 has been reduced to enable a gripping mechanism, not shown, to grasp the point. A mandrel 15 supports the inside surface and controls the internal diameter of the tube as it is drawn.

' In accordance with our invention, tube 20 (FIG. 2) may be beveled at end 22. A point member 23 is prefonned by some suitable forming method such as forging or swaging. Point member 23 comprises a smaller diameter cylindrical portion 24 and a coaxial larger diameter cylindrical portion 25 connected by a symmetrical segment 26 of any suitable geometric shape. The point member is fixedly attached to tube 20 by friction welding.

Machined point member 30 (FIG. 3) comprises a solid cylinder 31, an optional gripping knob 32 and a cylindrical end portion 33. The point member is friction-welded to tube end 34. The knob 32 provides a positive mechanical seat for the gripper jaws. Cylinder 31, being solid, is not subject to being crushed. Point member 40 (FIG. 4) is similar to the point member 23, but inclues a flared end 42 to give the gripper jaws a positive seat.

Point member 50 (FIG. 5) comprises a cone 52, cylindrical tank 53, and gripping ridges 55. After reduction of each tube is completed, this point and point member 60 (FIG. 6) can be used as points of smaller tubes until they can no longer enter a die, or until the work-hardening from so many reductions causes them to become so brittle that they break.

Point member 60 comprises a series of coaxial cylinders starting with shank 62, and each succeeding cylinder from the shank has a greater diameter. A radius 63 or bevel 64 may be machined on the corner of each cylinder for ease in entering a drawing die.

It is readily apparent that alternative point configurations are limitless. However, each point would be characterized by the following:

The point member can be fabricated from an alloy steel of any desired strength. Thus a high strength alloy would reduce the possibility of a point member breaking during the drawing operation. Conversely, a low strength alloy would provide a safety valve, in that the point member would break rather than the more expensive drawing equipment.

Since the tube to be drawn has not been heated to forging temperature, no heat treatment is required prior to cold drawing.

The point member has an easily reproducibe symmetry because its production can be subject to quality control.

Attachment of the point member is a readily automated procedure, and can be done in line.

The point member may be cut from the tube and reused after cold drawing is completed. If the final diameter of the tube is reduced by cold working, the point member can subsequently be used to draw a pipe with smaller diameter.

From the foregoing, it is readily apparent that we have provided an improved method of pointing a tube end for cold drawing, which method precludes the ne cessity for-heat treating prior to drawing, and is readily adaptable to automated operation. We have also provided a point member that is geometrically uniform, and in axial alignment with the tube to be drawn. The

' point member can also be drawn through many dies before it must be discarded.

We claim: l. A method of starting a tube through a colddrawing die, comprising:

pre-forming a round point member, having a larger end and a smaller end, the smaller endof said member having an external diameter less than the opening of said drawing die, the larger end of said member having an external diamter greater than the opening of said drawing die and greater than the internal diameter of said tube but no greater than the external diameter of said tube;

co-axially attaching the larger end of said point member to the end of said tube to be drawn, the mating surfaces of said point member and said tube being substantially normal to the longitudinal axes of said point member and said tube; and

introducing said point member to said cold-drawing die.

2. A method as defined in claim 1, in which attachment of said point member to said tube is accomplished by friction welding. 

